Carburetor



Aug. 24, 1948. F, BARFOD 2,447,791

- CARIBURE'I'OR Filed Aug. 25, 1943 IN VEN TUB FEEDER/K (BARFOD PatentedAug. 24, 1948 UNITED STATES PATENT. OFFICE CARBUBETOR v Frederik Barfod,South Bend, Ind., minor to Bendix Aviation Corporation, South Bend,Ind., a corporation of Delaware Application August 25, 1943, Serial No.499,987

3 Claims. (01. 261-69) This invention relates to fuel feeding systemsfor internal combustion engines and more particularly to devices orsystems in which liquid fuel vide a device of this character whereinthere is is supplied thereto under super-atmospheric pressure.

One of the principal objects of the invention is to provide a simplifieddevice of this character which may be built at reasonable cost and whichis capable of accurately regulating the fuel supply to maintain a properfuel to air ratio through wide ranges of engine load and speed.

Another object of the invention is to eliminate boiling of the fuelunder high temperature or altitude conditions, such as are experiencedwith an aircraft engine, to thereby insure accurate metering. This isaccomplished by maintaining the fuel under positive pressure until it isdischarged into the air supply to form a combustible mixture for theengine.

Still another object of the invention is to finely atomize the fueldischarged into the air stream to produce an improved mixture capable ofbeing readily ignited even though the engine is cold.

' A further object of the invention is to provide a device of thischaracter adapted to improve the fuel distribution in the air stream.This is effected by directing the air entering the induction passageradially toward the discharge end of the fuel nozzle from a plurality ofsides thereof.

It is a further object of the invention to provide a fuel feeding deviceor system which will operate properly in any position so that wheninstalled on an aircraft engine the latter will be properly suppliedwith fuel regardless of the position of flight.

A still further object of the invention is to provide a device or systemof this character wherein the fuel is supplied to the nozzle at asubstantially constant superatmospheric pressure, and the metering ofthe fuel is controlled by said fuel pres-' sure, a counterbalancingpressure and by suction resulting from operation of the engine.

A further object of the invention is to provide a device of thischaracter wherein a fluid control valve is urged in opposite directionsby normally substantially balanced pressure exerting means ofsubstantially constant pressures and the opening of said valve iscontrolled by variable fluid pressure means adapted to varythe pressureof one of said balanced pressure means.

Another object of the invention is to provide a device of this characterwherein the variable pressure controlling the fuel valve is derived frominduction passage suction which may be anterior to the throttle valve.

Still another object of the invention is to proa suction connection to aventuriand an idling connection may be includedin the system which mayinclude a port or ports adjacent the edge of the valve when closed, saidports, if desired, being on opposite sides of the closed throttle valve.

Other objects and advantages of the invention will be readily apparentto one skilled in the art from the following description taken inconnection with the accompanying drawing. which representsa preferredembodiment. After considering this embodiment skilled persons willunderstand that many variations may be made without departing from theprinciples disclosed; and I contemplate the employment of anystructures, arrangements, or modes of operation that are properly withinthe scope of the appended claims. The drawing diagrammaticallyillustrates a fuel feeding system embodying the present invention, partsof said system being in section.

Referring more particularly to the drawing there is shown adowndraftcarburetor' indicated generally at I0 and including aninduction passage l2 attached to the intake manifold ii of an internalcombustion engine (not shown), said induction passage having a mixtureoutlet ll.

controlled by a throttle valve it of well known character mounted on athrottle shaft It. Attached to the upper end of the induction passage I2is a riser member 20 having a plurality-of circumferentially spaced airinlet openings 22. Secured to the upper end of the riser member is afuel nozzle unit indicated generally at 24 having a fuel connection 26with a fuel pump 28 which may be of any commercial type adapted todeliver fuel at substantially a constant pressure, said fuel pump beingdriven by any suitable means, such as the engine equipped with thepresent invention, and said pump is connected with a fuel tank 30 bymeans of a fuel" conduit 32. Although any type of constant pressure pumpmay be used, the one shown is of the sliding vane type utilizing abypass 34 from the outlet or discharge side of the pump to the inletside for bypassing fuel from said outlet side of the pump to the inletside to maintain a constant outlet pressure. This is effected by a valve36 having a movable valve member 38 urged to the closed position by aspring 39, the tension ofsaid spring .39 being predetermined and socalibrated that when the discharge pressure of the pump rises above saidpredetermined value the valve will open-to permit passage of fuel fromthe outlet side of the pump to the inlet side thereby prerates thehollow interior of the nozzle unit into a fuel chamber 44 and an air orsuction chamber 46. The fuel conduit 26 is connected with the fuelchamber 44 by a passage 48 having a calibrated metering jet meansillustrated diagrammatically by the restriction or Jet 58. Although buta single restriction 58 is shown for illustrativepurposes, it will beunderstood that a varable orifice or a plurality of orifices may be usedwhereby the total effective area of the metering jet means may be variedto provide a lean or rich mixture or power enrichment, an increase inthe area resulting in an increase in richness as will be apparenthereinafter.

Fuel is discharged from chamber 44 through a nozzle 5| having adischarge passage 52 substantially axially arranged with respect to theinduction passage 2 and the discharge end of said passage 52 is insubstantially the same plane as that of the air inlets 22 so that thefuel discharged is broken up or atomized by the streams of entering airfrom a plurality of sides. Discharge of fuel from passage 52 iscontrolled by a valve comprising a movable valve member 58 cooperatingwith a valve seat 54. The valve member 53 is secured to the diaphragm 48by any suitable means such as riveting at 55 and said valve member 58 isslidable within a valve guide diaphragm by the riveted portion 55 and aspring cup 66 secured to a screw 88 threadably received in a wall of thecasing member 42 whereby the cup 85 may 'be manually adjusted to varythe tension or pressure of spring 62 on the diaphragm 43. The chamber 48has a priming connection with the induction passage I2 which comprises aconduit 18, with a tube 12 having a calibrated restriction 88 therein,said tube 12 being connected with the interior of a small 'venturi 14disposed within the induction passage I2, the downstream end of thesmall venturi |4 being disposed within the restricted portion of a largeventuri 18. It is to be noted that the venturis are disposed beneath thefuel discharge nozzle 5| and in the line of discharge thereof so thatfuel sprayed from said nozzle 5| is uniformly directed toward saidventuris. If desired, there may be included in "the system means forproviding a supply of idling fuel for the engine including at least oneconnection from the chamber 45 to the induction passage at a pointadjacent the throttle valve when closed. This connection preferablyincludes a passage 88 having branches 88 and 88 terminating in ports 92and 94 respectively on opposite sides of the leading edge of thethrottle valve l5 when closed. The passage 86 may be. connected by aconduit 84 with the conduit 18 between the calibrated restriction 88 andthe 4 chamber 48; and if desired there may be a restriction 88 of fixedsize in the branch passage 84 and an adjustable needle valve 88 for thebranch passage 82.

Operation Fuel is supplied to the fuel conduit 28, leading to thechamber 44 of the nozzle unit 24', under substantially constantsuperatmospheric pressure and the tension or pressure of spring 82 onthe diaphragm 48 is, adjusted by means of the screw 58 so that saidspring tension or force urging the valve toward closed position issubstantially equal in value to the force created by fuel at pumppressure in chamber 44 on the opposite side of said diaphragm urging thevalve toward open position; and it is to be understood that theeffective pressures of the spring and the fuel on the diaphragm normallycounterbalance each other when the air pressure in chamber 48 isatmospheric, at which time the fuel valve 58 is maintained closed.

During operation, the air flow through the induction passage will createa suction in venturi 14 which will vary in accordance with the quantityof air being supplied to the engine. This suction is transmitted throughpassage 18 to chamber 48 and opens valve 58 until the rate of fuelflowis such that the pressure of the fuel in chamber 44 is reduced, byvirtue of the metering jet means 58, an amount equal to the decrease inpressure in chamber 48. .The differential in the fuel pressures onopposite sides of the meter ing Jet 58 thus varies directly inaccordance with the suction in chamber 46, and consequently the quantityof fuel supplied to the engine will be controlled in constant proportionto the quantity of air, unless the suction in chamber 45 is furthermodified by means such as the idle ports 92, 94' whose function will nowbe described.

During idling, it is of course desirable to provide a somewhat enrichedmixture. This is accomplished by the ports 82 and 84 which, due to thehigh suction prevailing posterior to the throttle during idling, tend toincrease the suction in passage 18 above that which would normally existdue to the flow of air through the venturi 14. The ports 82 and 84 thusincrease the suction in chamber 48 and therefore increase the quantityof fuel being supplied at idling, to thereby enrich the mixture.

By the use of idling suction ports positioned on opposite sides of thethrottle when closed, and by properly proportioning their relative sizesand the size of restriction 88, any desired enrichment characteristicmaybe obtained at idling and through the near-idling range. It will bereadily apparent that instead of two idling ports,

r three or more ports, or a slot of constant or varying width extendinglongitudinally of the induction passage and adjacent the leading edge ofthe throttle when in idling position, could be used.

It will be understood that the effective area of the fuel metering jetsystem determines the quantity of fuel which will be supplied to theengine for any given suction in chamber 46. As a consetem may thereforebe used with the device of the instant invention to automatically varythe richness of the mixture to produce a rich mixture during high poweroperation, or a lean mixture during light load operation, or tootherwise var the richness of the mixture under particular conditions ofoperation of the engine.

It will be apparent from the foregoing that a very simple inexpensivepressure type carburetor has been provided utilizing but a singlediaphragm and valve but capable of accurate fuel-to-air proportioning.It is thought that the invention and many of its other attendantadvantages will be understood from the foregoing description and thoughsaid invention has been illustrated in connection with but onemodification thereof it will be apparent that various changes may bemade in .the form, construction and arrangement of the parts withoutdeparting from the spirit and scope of the invention or sacrificing allof its material advantages, the form hereinbefore described being merelya preferred embodiment.

I claim:

1. In a fuel supply system for an internal combustion engine: adowndraft induction passage having a plurality of circumferentiallyarranged air inlets in the upper end thereof; a throttle valve adjacentthe opposite end of said induction passage; a plurality of venturisanterior to the throttle valve; a nozzle unit disposed adjacent theupper end of the induction passage and having a chamber therein; adiaphragm separating the chamber into a fuel compartment and an aircompartment; a discharge nozzle connected with the fuel compartments sopositioned that fuel discharged therefrom receives the impact of the airentering the induction passage from the air inlets: a fuel control valveconnected with the diaphragm and controlling the discharge passage ofthe nozzle anterior to the discharge end thereof, said discharge endbeing unobstructed posterior to the valve; an engine driven means forsupplying fuel at substantially a constant pressure; a conduitconnecting said means with the fuel chamber; a metering jet system insaid conduit anterior to the fuel chamber, the diaphragm being urged ina directiontending to open the fuel valve by pressure of fuel in saidfuel chamber; a spring disposed in the .air chamber and urging thediaphragm in a direction tending to clos the fuel valve with a forcesubstantially equal to the full pressure of said means; means formanually adjusting the tension of the spring; means including a conduitfor connecting the air chamber with the small venturi; a restriction inthe last mentioned conduit; means for connecting said air chamber withthe induction pasage adjacent to and on opposite sides of the leadingedge of the throttle valve; a restriction of fixed size in theconnection adjacent to and anterior to the throttle valve; and anadJustable restriction in the connection posterior to the throttlevalve.

2. In a fuel supply system for an internal combustion engine, a chargeforming device having an induction passage provided with a plurality ofannularly spaced air inlets, a fuel discharge nozzle having itsdischarge end located in substantially the same plane as the air inlets,a fuel metering device anterior to said nozzle, engine driven means forsupplying fuel to the metering device at substantially a constantsuper-atmospheric pressure, a valve controlling the discharge of fuelfrom said nozzle, a pressure-responsive element connected to said valveand urged in a valve-opening direction by the pressure of fuel posteriorto the metering device, said nozzle being open at all times beyond thevalve, a spring operatively associated with said pressure-responsivemeans and urging the valve toward closed position with a forcesubstantially equal to that of the full pressure of said engine-drivenmeans, and means for exerting suction on said pressure-responsive meansto vary the force of the yielding means, the suction being derived froma pressure varying with variations in the flow of air to the engine.

3. In a fuel supply system for an internal combustion engine having' anair induction passage and a fuel conduit for supplying fuel under pressure to said passage, a metering restriction in said conduit, means formaintaining the fuel insaid conduit anterior to said restriction at asubstantially constant pressure, a chamber for metered fuel in saidconduit posterior to said restriction, said conduit terminating in afuel discharge nozzle connecting said chamber with the inductionpassage, a plurality of air inlets in the induction passage adapted todirect air into the passage in converging streams adjacent the point ofdischarge of said nozzle, a valve controlling said nozzle, a diaphragmconnected to said valve and forming a movable wall of said chamber, thepressure of fuel on said diaphragm posterior to said restriction tendingto open said valve, a spring tending to close said valve with a pressuresubstantially equal to the fuel pressure to be maintained in said fuelconduit anterior to said restriction, and means for modifying the actionof said spring by a pressure decreasing with an increase in air flow tothe engine.

FREDERIK BARFOD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

